Emergency vehicles currently use loud sirens and flashing lights for alerting other road users to the presence of approaching emergency vehicles. However, audio alerts are often unreliable. Vehicles are often noisy environments created by conversation, radios and CD players which prevent the driver from being aware of an audio alert from an approaching emergency vehicle.
Visual alerts are also be unreliable as they rely on driver awareness (which is often reduced in situations such as traffic jams when cooperation between emergency vehicles and other road users is essential). Visual and audio alerts have a very limited range of effectiveness due to the limited range of awareness associated with visual and audio alerts. Traffic congestion also inevitably builds up near to the destination of the emergency vehicle (such as an accident, fire, etc.), causing further delays to the emergency vehicle and limiting the effectiveness of the services associated with the emergency vehicle.